1. Field of the Invention
This invention relates to the production of aldehydes and alcohols and relates particularly to the production of these oxygenated compounds by reacting an olefin with hydrogen and carbon monoxide in the presence of a catalyst.
2. Description of the Prior Art
The reaction of an olefin with hydrogen and carbon monoxide is the well-known hydroformylation reaction. It is also known as the oxo reaction. Catalysts employed for this reaction have included cobalt and rhodium carbonyls which are soluble in the reaction mixture when the reaction is carried out in the liquid phase. Soluble ruthenium catalysts have also been used. Additionally, cobalt and rhodium contained in crystalline alumina-silicates, these being insoluble in the liquid reaction mixture, have been suggested.
In the prior art processes of reacting an olefin with hydrogen and carbon monoxide, the use of homogeneous metal-containing catalysts, i.e., soluble in the liquid reaction mixture, has presented difficulties. The recovery and regeneration of the dissolved metal catalysts from the liquid reaction products require special equipment and handling which add significantly to the complexity and cost of the operations. Furthermore, small losses in recovering, regenerating, and recycling the soluble catalysts are unavoidable. In the case of expensive catalysts, especially those containing rhodium, these losses increase the cost of the operation substantially and to a point where the operation may not be economically justified.
Means have heretofore been sought to overcome the disadvantages inherent in the use of homogeneous catalysts. For example, it has been proposed to use metals such as rhodium or cobalt on a solid support, as disclosed in the article by Pruett et al., Journal of Organic Chemistry, Vol. 34, p. 327 (February, 1969). However, in these instances, the active catalyst, believed to be a metal carbonyl complex, is formed from the metal under the reaction conditions, and the complex is soluble in the liquid reaction medium. It has also been proposed, as in U.S. Pat. No. 3,352,924, to use as a solid catalyst in the hydroformylation reaction a crystalline alumina-silicate containing rhodium or cobalt ions. However, such catalysts, when used in a continuous operation, lose their initial activity after some time and then cease to function. It has been further proposed to deposit selected rhodium complexes on particles of inert solids such as carbon, silica, clays or metal oxides, for example, by impregnation, as in U.S. Pat. No. 3,487,112, to produce a hydroformylation catalyst. Under the conditions of the hydroformylation reaction, however, the complexes, and their carbonyl reaction products, are soluble in the liquid reaction medium.
The disadvantages inherent in the use of homogeneous catalysts can be avoided by carrying out the reactions in the gas phase. This, however, limits the type of reactants, or reaction conditions, or both, that may be employed. Thus, since the hydroformylation reaction occurs at quite low temperatures, a severe restriction is imposed on the usable partial pressure of the reagents, and of the products. It also limits the reaction to reactants of low boiling point and low molecular weight.
Further, with respect to various of the above-mentioned catalysts and others heretofore employed, difficulty has been encountered by the reaction being insufficiently selective to conversion of the olefin to aldehyde or alcohol, a significant portion of the olefin feed being hydrogenated to form a saturated compound.